UNITED NATIONS, April 8 (Reuters) - Human rights violations by Syrian government forces "far outweigh" those by armed opposition groups, U.N. human rights chief Navi Pillay said on Tuesday, prompting the Syrian U.N. envoy to accuse her of acting like an irresponsible "lunatic."

Pillay briefed the 15-member U.N. Security Council on the human rights situations in Syria, Central African Republic, South Sudan, Mali and Libya. She again called for the situation in Syria, which has been ravaged by a three-year civil war, to be referred to the International Criminal Court.

Pillay said monitors in her office and investigators with the U.N. commission of inquiry in Syria, led by Paulo Pinheiro, had consistently blamed both parties to the Syrian conflict for human rights violations "but you cannot compare the two."

"Clearly the actions of the forces of the government far outweigh the violations (by rebels)," Pillay told reporters. "It's the government that is mostly responsible for the violations and all these perpetrators should be identified and can if there's a referral to the International Criminal Court."

"There has to be justice and accountability and the situation in Syria should not be allowed to slip through the cracks," she said after briefing the Security Council.

The council has so far been unable to refer Syria to the International Criminal Court because Russia is opposed to the move, diplomats say. Russia, supported by China, has shielded ally Syria from council action during the civil war.

Syrian U.N. Ambassador Bashar Ja'afari dismissed Pillay's accusations against Syrian government forces as false and lacking credibility because Pillay and U.N. investigators had not visited Syria during the conflict.

"LUNATIC"

"(Pillay) has become lunatic in her action and is behaving irresponsibly," Ja'afari told reporters. "She's manipulating, bluffing the truth and she is biased. She is using her position in favor of making further pressure on the Syrian government."

"She doesn't have any credible information with regard to what's going on in Syria," he said after the council briefing.

Pillay told the Security Council that her office was due to issue a report later this week documenting torture by both government forces and opposition groups, said a diplomat who attended the briefing, speaking on condition of anonymity.

She recounted to the council the case of a 26-year-old woman who was tortured by government forces, said the diplomat. The woman was hung against a wall for three days, some of her teeth were pulled out and she was sexually assaulted, Pillay said.

In a report to the U.N. Human Rights Council last month, Pinheiro's investigators said they have expanded their list of suspected war criminals from both sides and the evidence was solid enough to prepare an indictment.

Syria's civil war has killed more than 150,000 people, a third of them civilians, and caused millions to flee.

U.N. Secretary-General Ban Ki-moon demanded that the warring parties in Syria stop violence against civilians, including indiscriminate shelling and air attacks on civilian areas. He also expressed concern that groups listed as terrorist organizations by the U.N. Security Council continue to "brutalize" civilians.

"There is a belief by too many in Syria and beyond that this conflict can be won militarily. More violence will only bring more suffering and instability to Syria and sow chaos in the region," Ban said in a statement late on Monday. (Reporting by Michelle Nichols; Editing by Lisa Shumaker)